Compositions and methods for controlling the growth of microbials in aqueous media

ABSTRACT

Compositions and methods are disclosed for sanitizing aqueous media, which combine a chlorine-source composition and a glycoluril-source composition. The compositions are added together or separately, continuously or periodically, and by any of a variety of methods. The glycoluril compound stabilizes the chlorine and prolongs its useful life as a microbicidal agent.

This application is a continuation of application Ser. No. 08/069,122,filed May 28, 1993, now abandoned, which is a continuation of Ser. No.07/755,822 filed Sep. 6, 1991, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention:

The present invention relates to the field of disinfectant systems forswimming pool and spa water, cooling tower water, and other aqueousmedia. More particularly, the invention relates to systems utilizingchlorine as a disinfectant, and to compositions and methods forstabilizing and increasing the useful life of the chlorine in suchsystems.

2. Description of the Prior Art:

The steady increase in the number of swimming pools in use each year hasgiven rise to the need for a more effective, safe, and convenientchemical sanitation. Chlorine in various forms is the most widely usedchemical for this purpose, since it is both economical and also highlyeffective in bacteria and algae control. However, its efficiency andeffectiveness vary, and depend upon the method used to introduce theelement into the pool water and the type of chlorine compound used.Gaseous chlorine, hypochlorites, and chlorinated organics are all usedfor swimming pool sanitation and exhibit different types of chlorineresiduals and various degrees of bactericidal activity, algicidalactivity, and chemical consumption. In addition, such external variablesas pool usage and climatic conditions have significant effects upon theefficiency of the sanitizing action.

Various approaches have been proposed in the prior art for stabilizingthe chlorine in disinfecting systems. For example, in U.S. Pat. No.2,988,471, issued to Robert J. Fuchs et al. on Jun. 13, 1961, there isdescribed a method for stabilizing chlorine in aqueous solutions againstdecomposition by exposure to ultraviolet light or by contact with ironand copper. The method involves adding to the aqueous solution cyanuricacid, ammelide or a salt thereof. The loss of active chlorine isreported to be substantially reduced when the weight concentration ofthe cyanuric acid is greater than the weight concentration of theavailable chlorine. The use of cyanuric acid to substantially reduce theloss of active chlorine in aqueous systems exposed to sunlight, forexample in swimming pools, has received wide commercial acceptance. Seealso, e.g., U.S. Pat. No. 4,187,293, issued to Nelson on Feb. 5, 1980.

Although satisfactory results are achieved with the use of cyanuricacid, serious problems exist. One problem is the relatively short halflife of active chlorine when exposed to sunlight. At 50 ppm cyanuricacid, the chlorine half-life is only seven hours. On a normal sunny daythe majority of the chlorine sanitizer is depleted rapidly.

A second problem that exists is the build up of cyanuric acid in theaqueous system. It is recommended that atypically high concentrations ofcyanuric acid be-reduced to below 100 ppm by partial drainage of thepool water and refilling with fresh water. In fact, in commercial pooloperations some health officials will close a pool if the cyanuric acidexceeds 70 ppm. Kirk-othmer Encyclopedia of Chemical Technology, 3rd Ed.Vol. 24, p. 430.

In contrast to the present invention, halogenated glycolurils have beenproposed in the prior art as the source of disinfecting chlorine. Forexample, in U.S. Pat. No. 3,165,521, issued to Slezak et al. on Jan. 12,1965, a method for sanitizing aqueous water systems is disclosed inwhich haloglycolurils are used as the source of free chlorine tofunction as a swimming pool sanitizer. The amount of compound used isthat which provides satisfactory disinfecting levels of residualchlorine, i.e. about 0.4 to 0.8 ppm. The use of haloglycolurils as thesanitizing agent in swimming pools is also disclosed in U.S. Pat. No.3,165,521, issued to Slezak. The use of polyhaloglycolurils forcontrolling algae in water is disclosed in U.S. Pat. No. 3,252,901,issued to Zettler. The use of chlorinated glycolurils in the treatmentof sewage is disclosed in U.S. Pat. No. 3,445,383, issued to Horvath etal.

The preparation of glycoluril is disclosed in U.S. Pat. No. 2,731,472,issued to Reibnitz. U.S. Pat. No. 3,071,591, issued to Paterson,discloses a method for the preparation of N-halogenated glycolurilscontaining both bromine and chlorine for use as disinfecting agents.

Various other sanitizing approaches have involved the use of certainsubstituted glycolurils. The use of substituted glycolurils incombination with trichlorocyanuric acid and sodium stearate insanitizing sticks is disclosed in U.S. Pat. No. 3,342,674, issued toKowalski. The use of chlorinated glycolurils in combination with ametallic hypochlorite in treating sewage is disclosed in U.S. Pat. No.3,629,408, issued to Horvath. U.S. Pat. No. 3,187,004, issued to Slezak,discloses the synthesis of alkyl and aryl substituted glycolurils andtheir use in sanitizing swimming pools. This patent discloses the use ofN-halogenated glycolurils with alkaline metal salts.

While these various approaches to sanitizing swimming pool water and thelike have been proposed in the prior art, there has remained asubstantial need for improved compositions and methods providingsustained disinfection of aqueous media. Though many in the past havepursued chlorine-based systems, the useful life of chlorine in suchsystems has remained undesirably short. Viable commercial approacheshave not been forthcoming, and theoretical approaches have beenabandoned. The present invention satisfies the need for a stable,effective chlorine-based disinfectant system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the effect of glycoluril on TCCA at 2 min. contact time.

FIG. 2 shows an airstripping apparatus constructed to determine theeffect of glycoluril upon the volitility of chlorine and chloramines.

FIG. 3 shows the effect of glycouril on chlorine volitization afterammonium chloride was subequently added to a glycoluril and chlorinemixture.

FIG. 4 shows the effects of addition of unsubstituted glycoluril onchlorine volitization.

FIG. 5 shows effects of glycoluril on TCCA; 2.5 ppm Cl2/5, 10, 25 ppmglycoluril.

FIG. 6 shows the efficacy of 1.5 mg/l TAC in the presence of 7 mg/lglycoluril with and without cyanuric acid.

SUMMARY OF THE INVENTION

It is an aspect of the present invention that glycoluril has been foundto stabilize chlorine added for disinfection of an aqueous media, thusprolonging the useful life of the added chlorine compounds. Glycolurilcan be added at any time, either before or after the addition of thechlorine-source composition, and is maintained at the level determinedto provide a desired stabilizing effect for the chlorine.

Aqueous systems, such as swimming pool water, operated on treatmentprograms based on this disclosure allow for efficient use of thechlorine sanitizer by substantially increasing the chlorine half-life.Several advantages are thereby obtained. Cost savings are realizedbecause the swimming pool water will consume up to 50% less chlorine ina normal pool season. In addition, the reduction of the amount ofchlorine consumed will reduce the build up of certain chemicals, such ascyanuric acid, associated with the use of particular chlorine-sourcecompositions, for example trichloro-s-triazinetrione (TCCA).

Controlling the level of the chlorine-source composition and glycolurilin the ranges taught in this disclosure allows for the operation of avery effective treatment program for aqueous systems.

Further objectives of the present invention include providingcompositions and methods for reducing the presence of trihalomethanesand the offensive odoring associated with certain chlorine-sourcecompositions, such as TCCA.

DESCRIPTION OF THE PREFERRED EMBODIMENT

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the preferred embodiment of theinvention and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended, such alterations, modifications andfurther applications of the principles of the invention beingcontemplated as would normally occur to one skilled in the art to whichthe invention relates.

The use of chlorine as a disinfectant for swimming pool water, coolingtower water and other aqueous media has been well known for many years.In these environments, chlorine compounds are continuously orperiodically added to the water to maintain a microbicidal concentrationof chlorine. Without periodic addition, the effective chlorineconcentration in the water will decrease due to dissipation, reaction,conversion into unusuable forms, etc. In accordance with past methods,the useful life of added chlorine has been undesirably short, and therehas remained an unsatisfied need for extending the effective life ofadded chlorine compounds.

The present invention provides compositions, systems and methods forextending the useful life of chlorine provided to aqueous media fordisinfecting purposes. In particular, the present invention utilizes theactivity of glycoluril as a stabilizer for chlorine in an aqueousenvironment. Addition of the glycoluril and chlorine compositions may beat the same or different times, continuous or periodic, and by any of avariety of addition methods. The presence of the glycoluril at astabilizing concentration suited to the chlorine concentration willresult in an extended effective life for the chlorine in a statesuitable for microbicidal activity. For example, the half-life fortrichloro-s-triazinetrione (TCCA) in a given system is about 6-7 hours,whereas use of glycoluril in the system extends the half-life to about25 hours.

The present invention utilizes a glycoluril-source composition thatprovides glycoluril to stabilize and prolong the useful life of thechlorine. Glycoluril-source compositions useful with the presentinvention include any which will contribute a glycoluril compoundcompatible with and useful for stabilizing the chlorine, and suitablefor the aqueous media being treated. Substitution on the glycoluril isnot critical, provided that the substituents do not interfere with theutility of the glycoluril in the manner described herein.

As used herein, the term "glycoluril" encompasses a compound whichincludes the basic formula: ##STR1## in which a is either 0 or 1. Asused herein, the compound consisting solely of the structure shown informula I is referred to as unsubstituted glycoluril. In addition to theunsubstituted glycoluril (I), useful glycoluril-source compositionsinclude the chloro, alkyl and phenyl substituted glycolurils. The termglycoluril thus includes compounds of the foregoing basic structure (I),as well as compounds including substituents such as alkyl, phenyl andchloro groups at available bonding sites. Bromo-substituted glycolurilsmay also be useful in certain applications, although the presence of thebromine substituent may interfere in some systems with the utility ofthe glycoluril as a chlorine stabilizer.

More specifically, preferred glycoluril-source compositions includeglycolurils having the following structure: ##STR2## in which R and R₁are independently selected from the group consisting of hydrogen, loweralkyl radicals of from 1 to 4 carbon atoms, and phenyl; each X is eitherhydrogen, chlorine or bromine; and a is either 0 or 1. It is preferredthat R and R₁ be either hydrogen or methyl, as alkyl radicals withlonger carbon lengths render the glycolurils less soluble in water.

The chlorine concentration in the aqueous media may be obtained from anysuitable source which provides hypochlorous acid (HOCl) to the water.Chlorine-source compositions may include both inorganic and organicmaterials. Useful inorganic materials include molecular chlorine,lithium hypochlorite (LiOCl), calcium hypochlorite (Ca(OCl)₂, sodiumhypochlorite (NaOCl) and hypochlorous acid (HOCl). Organic sources mayinclude, for example, bromochlorodimethylhydantoin (BCDMH),dichlorodimethylhydantoin (DCDMH) or compositions based on cyanuricacid, such as sodium or potassium dichloro-s-triazinetrione ortrichloro-s-triazinetrione (TCCA). These compounds are readily availablein commercial form. TCCA, for example, is available from severaldifferent suppliers, including Monsanto Chemical Co. under the nameACL-90. The most preferred composition is TCCA. However, it will beappreciated that the chlorine source is not critical to the presentinvention, provided that the source is compatible with the aqueous mediasystem being treated and is stabilized by the glycoluril compound whichis utilized.

A wide variety of aqueous media may be treated by the present invention.In general, any aqueous media which is effectively treated withchlorine, and which is compatible with the described chemicals, can betreated. Typical systems for which the present invention is usefulinclude swimming pools, spas, hot tubs and health related baths,decorative fountains, recirculating water cooling systems, dehumidifiersystems, ponds, reservoirs and waste water systems.

The concentrations of glycoluril and chlorine will vary depending on theaqueous media being treated. An advantage of the present invention isthat the level of glycoluril can be readily matched to the desiredchlorine concentration effective for the given aqueous system. Theselected glycoluril level will facilitate maintaining the desiredmicrobicidal level of the chlorine in the water.

The appropriate concentrations of the chlorine, and therefore of theglycoluril, will also differ based upon the conditions attendant to theaqueous media. For example, effective levels may differ based upon suchfactors as the extent and nature of microbicidal activity needed, thepresence of other treatment chemicals, and conditions of use such astemperature, amount of sunlight, pH and the like. Generally, any factorswhich will affect the stability of the chlorine will have an impact onthe desired glycoluril levels. The present invention contemplates thatthe desired level of chlorine and of glycoluril can be readilydetermined by one of ordinary skill in the art without undueexperimentation, and specific concentrations therefore are not specifiedherein for each of the variety of treatable aqueous systems.

The level of glycoluril in the water is that which provides an effectiveconcentration of glycoluril to usefully stabilize the chlorine presentin the system. Typical concentrations of glycoluril effective asdescribed will range from about 0.1 to about 40.0 ppm of glycoluril inthe water. More preferably, the glycoluril is present in the water atfrom about 1.0 to about 10.0 ppm, with 3.0-7.0 ppm being most preferredfor many applications.

In some instances, it may be desirable to provide levels of glycolurilas high as 100 ppm, such as upon initial treatment of a pool. In thisway, the level of glycoluril would remain at an effective level for aprolonged period of time. Such high levels of glycoluril may also beused in combination with particularly high levels of chlorine in thewater.

The concentration of the chlorine in the water is that which provides aneffective level of chlorine for the degree of microbicidal activitydesired for the given aqueous media. The term total available chlorineis used herein to include both free chlorine and combined chlorine.Typically, a suitable concentration of total available chlorine will bein excess of about 1.0 ppm, and preferably will range from about 1.0 toabout 5.0 ppm in the water. This is true, for example, in the case ofswimming pool water. By way of comparison, the desired total availablechlorine level in cooling tower water may differ, ranging from about 1.0to about 10.0 ppm of total available chlorine.

The present invention advantageously uses two separate compositions, oneprimarily providing the chlorine and the other primarily providing theglycoluril. The overall effect is that the glycoluril is maintained at alevel which stabilizes the chlorine and prolongs its life to reduce theamount and frequency of addition of the chlorine. Although certain formsof glycoluril-source compositions may include chlorine which will becontributed to the water, such forms of glycoluril are contemplated inthe present invention as primarily stabilizing compositions. Indeed, theamount of chlorine which can be added to the water through a chlorinatedform of glycoluril is typically either insufficient, or would requirethe use of amounts of chlorinated glycoluril which are otherwiseundesirable.

The glycoluril and chlorine compositions may be administered to theaqueous media in any manner effective to provide the desiredconcentrations of each compound. The glycoluril and chlorine may beadded to the water either together or separately, and eitherperiodically or continuously. The methods of application may vary withthe aqueous systems being treated, and the conditions of use pertinentthereto. In general, however, the methods are restricted only by theneed to maintain effective levels of the glycoluril and chlorine asdescribed, and may be any suited to the physical forms and particularcompounds employed. Existing disinfectant systems using chlorinecontemplate various methods for maintaining a desired level of thechlorine in an aqueous system. The present invention is advantageous inthat it may be readily adapted for use with a wide variety of suchexisting water treatment systems.

Typical methods of addition known in the art are broadcast and erosionmethods. Broadcasting refers to a direct addition of the chemical to theaqueous media in solid, typically granular, or liquid form. Compositionsuseful in the present invention may be readily prepared in forms andconcentrations convenient for broadcast application.

In the erosion method, compositions are fabricated into a solid-formmaterial which is contacted with the water in a manner to effect arelatively slow erosion of the solid material, thus gradually releasingthe composition into the water. The composition to be added is formed orcompressed into solid forms, such as tablets, sticks, pucks and othershapes, typically by a hydraulic or mechanical press. The solid-formmaterials may include inert fillers, such as sodium chloride or boricacid, that assist in the tabletting process. The solid material may alsocontain other ingredients such as tabletting aids, e.g., mold releaseagents, binders, corrosion inhibitors, scale inhibitors and othercomponents known to those skilled in the art.

Erosion methods are commonly employed in the prior art for introducingchlorine-source compositions into swimming pools, for example. Thechlorine composition, in solid form, is placed into a release devicethrough which water is circulated to erode the solid material. In thecase of a swimming pool, the tablet, stick or puck can be placed into askimmer basket, in-line or off-line feeders, or a floating releasedevice. While erosion may also be used for the glycoluril, it has beenfound that at least certain forms and types of glycoluril are not wellsuited to introduction by continuous erosion methods, because for theseforms the erosion method provides insufficient levels of glycoluril inthe water.

The glycoluril-source and chlorine-source compositions may be providedeither as two separate materials or as a physically combined product,depending on the form and intended manner of addition of the products.The provision of separate materials is preferred since the preparationof the compositions is thereby made simpler. Also, the methods andcompounds for adding the chlorine and the glycoluril are more flexible,for example permitting the use of liquid chlorine with a granularglycoluril composition, or permitting the continuous erosion addition ofthe chlorine and a periodic broadcasting of the glycoluril composition.The separate addition further enables the user to independently controlthe concentrations of the two compounds, which will be particularlyuseful if the water conditions result in a disparate depletion of onecompound compared to the other.

One particular method of maintaining the desired levels of chlorine andglycoluril is to provide a continuous addition of chlorine to the water,coupled with a periodic broadcast addition of the glycoluril compound.Additive glycoluril-source compositions can be readily formulated toprovide the desired levels of glycoluril in water upon addition ofprescribed amounts of material at indicated time intervals. For example,granular forms of the compositions may be readily prepared which givedesired concentrations of glycoluril when added to the water atintervals ranging from daily to every week or two. Naturally, thefrequency of addition will depend on the conditions to which the wateris subjected, and also on the amount, concentration and type ofglycoluril-source composition being added.

In a particular embodiment, the foregoing method may be enhanced byusing as the chlorine source a mixture of a chlorine compound and aglycoluril compound in a physical combination which facilitatessustained release of the chlorine compound into the water. Thus, atablet or stick form of chlorine-source material may be formulated whichalso includes a percentage of glycoluril. The glycoluril is formulatedwith the chlorine-source compound in the solid tablet or stick becauseit has been found that this will slow the erosion rate for the solidmaterial. This in turn extends the life of the solid material andreduces the frequency with which the tablets or sticks need to bereplaced. Consequently, the chlorine is added to the aqueous system at acontrolled and uniform rate over a longer period of time. The tablet inthis method will also contribute a certain amount of glycoluril to thewater, but the desired level of glycoluril may not be primarily obtainedfrom this source. Instead, a glycoluril-source compound is alsootherwise added into the water, such as by periodic broadcasting, tobring up and maintain the level of glycoluril in the water as desired.

According to this particular approach, the solid form tablets or sticksare formulated to include both chlorine and glycoluril source compounds.The chlorine compound is preferably selected from the group consistingof calcium hypochlorite, lithium hypochlorite, sodiumdichloro-s-triazinetrione, potassium dichloro-s-triazinetrione, andtrichloro-s-triazinetrione, and is present in an amount of from about50.0% to about 99.99% by weight. The glycoluril-source composition ispreferably selected from the group consisting of glycoluril,alkyl-substituted glycoluril, phenyl-substituted glycoluril, andchloro-substituted glycoluril, and is present in an amount of from about0.01% to about 50.0% by weight. Further discussion of such compositionsand their advantages is contained in the copending U.S. patentapplication, Ser. No. 652,983, filed Feb. 11, 1991, (now abandoned) andhereby incorporated by reference.

In accordance with this method, a particular embodiment of thesolid-form chlorine material comprises approximately 50-99.99% by weightof trichloro-s-triazinetrione and 0.01-50% by weight of glycoluril. In arelated embodiment, the solid-form material includes approximately50-99.9% by weight of trichloro-s-triazinetrione, 0.01-50% by weight ofglycoluril and 0-20% by weight of an alkali bromide salt. A preferredcomposition is 80-98% trichloro-s-triazinetrione (TCCA) and 2-20%glycoluril, or 70-90% trichloro-s-triazinetrione (TCCA), 5-10% sodium orpotassium bromide salt, and 5-20% glycoluril. Another preferred mixtureis 75-90% trichloro-s-triazinetrione, 5-10% potassium bromide and 5-20%glycoluril. The preferred glycolurils are unsubstituted glycoluril (I)and the chloroglycolurils, such as dichloroglycoluril andtetrachloroglycoluril. For most applications, glycoluril is preferred.

By way of particular example, the present invention is well suited touse in the treatment of swimming pool water. Current systems provide forthe addition of chlorine to maintain certain accepted levels, typically1 to 5 ppm of total available chlorine in the water. The presentinvention may be directly adapted for use in the variety of prior artsystems which utilize chlorine as a disinfectant by maintaining in suchsystems the indicated levels of glycoluril effective to stabilize thechlorine. The glycoluril also may be used with various other treatmentchemicals typically used in such systems, such as algicides, clarifiersand the like.

In addition, it is a feature of the present invention that thecompositions may be readily formulated to adapt their use in swimmingpool and other water systems. Swimming pool chemicals, for example, aretypically constituted to require the addition of convenient, prescribedamounts on a periodic basis, usually weekly. The chemicals utilized inthe present invention can be formulated on this basis. More preferably,the present invention prolongs the useful life of the chlorine to thepoint that the frequency of addition of chemicals may be extended beyondthe usual weekly basis, perhaps to once every two weeks or longer.

In a typical swimming pool application, the present invention wouldproceed as follows. About every week the user employs a prescribedamount of solid-form, chlorine-source tablets or sticks in an erosiondevice. Coupled with this is the periodic addition of theglycoluril-source composition, also preferably at weekly intervals. Thepresence of the glycoluril prolongs the useful life of the chlorine,reducing the frequency with which chlorine would otherwise have to beadded.

In an alternate method, the solid-form material includes thechlorine-source composition and glycoluril, for example about 95% TCCAand about 5% glycoluril. This formulation has a slowed erosion ratecompared to prior art chlorine products, and therefore will last up totwo weeks or more. The stabilizing of the chlorine effected by theglycoluril matches well with the extended erosion life of thesealternate tablets or sticks.

In addition, other chemicals may be used at the same time. Inparticular, it may be desirable to perform periodic "shocking" ofswimming pool or other water, a common step in prior art procedures. Inthis case, the shock may be conveniently performed, for example everytwo weeks, by adding a conventional material, such as sodiumdichlorocyanurate, at the same time as the addition of the glycoluril. Afull pool treatment system would then only require the addition ofalgicide, such as a quaternary ammonium compound, at the same two weekinterval, thus providing the user with a convenient system and methodfor the treatment of swimming pool water.

It has been observed that the ratio of glycoluril to total availablechlorine can be selected to optimize the duration and microbicidalefficacy of the chlorine. The amount of glycoluril in the water ispreferably limited to an extent appropriate to result in sufficienthydrolyzing of the chlorine. It is possible that the presence of toomuch glycoluril in comparison to the amount of total available chlorinewill affect the amount of chlorine in solution, and therefore themicrobicidal activity. In a sense, the glycoluril can be present in suchhigh amounts relative to the chlorine that the chlorine is made sostable as to reduce its microbicidal activity. For example, a standardhypochlorite solution will effectively kill 10⁶ bacteria in about 30seconds. A ratio of glycoluril to total available chlorine of about 5:1will result in a kill of about half of the bacteria in about twominutes, and higher ratios will further delay the kill time. Therefore,although water systems having higher ratios of glycoluril to totalavailable chlorine will still have microbicidal efficacy, theperformance will be diminished. It has been found that preferred ratiosof total available chlorine to glycoluril are from about 10:1 to about1:10, more preferably about 5:1 to about 1:5. While increased stabilityof chlorine is normally associated with decreased microbicidal activity,the present invention provides increased stability and desiredmicrobicidal activity.

The present invention is useful in a wide variety of applications. Aperson skilled in the art can readily determine the suitability of givenchlorine-source and glycoluril-source compositions for a particularaqueous system. The present invention may also be used in conjunctionwith a variety of other chemicals such as algicides, fungicides,clarifiers, pH adjusters, sequesterants and the like, and may be usedwith other chlorine stabilizers such as cyanuric acid, oxazolidinone,imidazolidinone, dimethylhydantoin, succinimide, toluenesulfonamide,sulfonamidobenzoic acid, melamine, dioxohexahydrotriazine,piperazinedione, and azodicarbonamidine.

In addition to the stabilization of chlorine, the present invention hasalso been found to provide several ancillary benefits to the aqueoussystems. For example, the addition of glycoluril in the amountsindicated reduces the offensive chloramine odor associated with certainchlorinating systems, such as those using TCCA. Similarly, thedevelopment of trihalomethanes is diminished in the presence of theglycoluril.

The following examples further illustrate the present invention, and areprovided as exemplary but not restrictive as to the scope of the presentinvention.

EXAMPLE 1

This example illustrates a method for treatment of water systems inaccordance with the present invention. This experiment was conducted todemonstrate the rate of loss of chlorine from solutions containingcyanuric acid, unsubstituted glycoluril and mixtures of the two. Thisexperiment was conducted under controlled conditions designed tosimulate conditions expected while operating a pool under full sunlight,

Four liter beakers containing 3500 mls of distilled water were placed ina Revco environment chamber equipped with a special ultra violet lampthat emits UV radiation at 295-340 nm. It is known that chlorine isdegraded by sunlight in the region of 295-340 nm. The water was balancedto the following specifications:

    ______________________________________                                        Calcium Hardness    200-250  ppm                                              Total Alkanlinity   100-135  ppm                                              pH                  7.2-7.4                                                   ______________________________________                                    

The test chemicals were then added as shown in Table I below:

                  TABLE I                                                         ______________________________________                                        Test Chemical Systems                                                                    Cyanuric Acid (CYA)                                                                          Glycoluril (G)                                      Beaker #1  (PPM)          (PPM)                                               ______________________________________                                        1          10             0                                                   2          50             0                                                   3          0              5                                                   4          0              10                                                  5          0              20                                                  6          50             5                                                   7          10             5                                                   8          50             10                                                  9          10             10                                                  10         50             20                                                  11         10             20                                                  ______________________________________                                    

The chlorine source for this study was trichloro-s-triazinetrione(TCCA), The chlorine demand on the test systems was met by adding excesschlorine and allowing the water to circulate overnight. The totalavailable chlorine level was adjusted the next morning with the TCCAstock solution.

The study was conducted over a 24 hour period, during which the beakerswere stirred continuously. The test solutions were exposed to theultraviolet radiation at 295-340 NM. The air and water temperatures werecontrolled at 80°-85° F., and the relative humidity at 80-100%. Watersamples were taken and the total available chlorine was measured using aHACH 3000 spectrophotometer and DPD colorimetric method. Due to thelarge number of beakers involved, the study was conducted in two runs.

                  TABLE II                                                        ______________________________________                                        Test Data - Run #1                                                            Beaker #    1        2      3      4    5                                     CYA/G (ppm) 10/0     50/0   0/5    0/10 0/20                                  Time        TCl.sub.2                                                                              TCl.sub.2                                                                            TCl.sub.2                                                                            TCl.sub.2                                                                          TCl.sub.2                             ______________________________________                                        Initial     1.80     1.78   1.79   1.82 1.80                                  1 hr        1.36     1.48   1.65   1.68 1.67                                  2 hr        1.08     1.25   1.54   1.56 1.53                                  3 hr        0.93     1.15   --     --   --                                    9 hr        0.25     0.68   1.26   1.31 1.31                                  19 hr       0.09     0.27   0.95   1.01 1.01                                  24 hr       0.06     0.15   0.80   0.87 0.89                                  ______________________________________                                    

                  TABLE III                                                       ______________________________________                                        Test Data - Run #2                                                            Beaker #  6       7      8     9     10    11                                 CYA/G (ppm)                                                                             0/5     10/5   50/10 10/10 50/20 10/20                              Time      TCl.sub.2                                                                             TCl.sub.2                                                                            TCl.sub.2                                                                           TCl.sub.2                                                                           TCl.sub.2                                                                           TCl.sub.2                          ______________________________________                                        Initial   1.50    1.51   1.52  1.53  1.60  1.5                                2 hr      1.27    1.38   1.36  1.43  1.45  1.4                                5 hr      1.15    1.24   1.29  1.31  1.34  1.3                                21 hr     0.89    0.82   0.94  0.98  0.98  0.9                                24 hr     0.61    0.80   0.88  0.91  0.90  0.9                                ______________________________________                                    

The objective of this study was to determine the rate of loss of totalavailable chlorine (TCl₂) from water systems containing cyanuric acid,unsubstituted glycoluril and mixtures of the two, when exposed toultraviolet light in the wavelength region of 295-340 nm. The chlorinehalf-life was determined by plotting % remaining total availablechlorine (TCl₂) vs. time (hours). As shown in TABLE IV, water systemscontaining both cyanuric acid and glycoluril exhibited a greaterhalf-life than water systems that contained only cyanuric acid, i.e.,the residual total available chlorine is dissipated more slowly in watersystems containing a combination of cyanuric acid and unsubstitutedglycoluril. Therefore, the chlorine is available for a longer period oftime, and its bactericidal and disinfecting activity is morecontinuously effective.

                  TABLE IV                                                        ______________________________________                                        Chlorine Half-life                                                                      CYA        Glycoluril                                               Beaker #1 (ppm)      (ppm)     t 1/2 (hrs)                                    ______________________________________                                        1         10         0         5.0                                            2         50         0         7.0                                            3         0          5         22.0                                           4         0          10        24.0                                           5         0          20        25.0                                           6         50         5         29.0                                           7         10         5         27.0                                           8         50         10        33.0                                           9         10         10        35.0                                           10        50         20        32.0                                           11        10         20        35.0                                           ______________________________________                                    

EXAMPLE 2

Solutions comprising 1 ppm, 2.5 ppm, and 5 ppm total available chlorinefrom TCCA, and unsubstituted glycoluril concentrations of 5, 10 and 25ppm, were tested for biocidal activity. These compositions were added to[test microbes] and [kill rate] was measured. As shown in FIG. 1, eachof the chlorine concentrations had greater biocidal activity at lowerglycoluril concentrations. Additionally, the rate of biocidal activityin the solution of 25 ppm unsubstituted glycoluril was slower than therates at 5 and 10 ppm unsubstituted glycoluril.

EXAMPLE 3

This example examines the potential for glycoluril to build-up throughnormal swimming pool usage. A 20,000 gallon vinyl in-ground pool wasfilled with water and balanced to the following specifications:

    ______________________________________                                        Calcium Hardness:   175      ppm                                              Total Alkalinity:   125      ppm                                              pH:                 7.4                                                       CYA:                35       ppm                                              ______________________________________                                    

The pool was maintained at 1 to 3 ppm total available chlorine usingcompressed, one-half pound TCCA sticks, and was shocked biweekly usinglithium hypochlorite to bring the total available chlorine level to 8ppm.

During the eight month test period the glycoluril level ranged from 1 to5 ppm. A sum of 1125 grams of unsubstituted glycoluril was added to thepool during the test period. At the end of the test period less than 1ppm of glycoluril was measured in the water.

EXAMPLE 4

This Example illustrates the ability of unsubstituted glycoluril toreduce the volatility of chlorine and inorganic chloramines from aqueoussystems, thereby reducing the offensive odors caused by the compounds.The results indicate that the unsubstituted glycoluril appears toeffectively retard the loss of free chlorine and inorganic chloraminesfrom aqueous systems.

To determine the effect of glycoluril upon the volatility of chlorineand chloramines, the airstripping apparatus shown in FIG. 2 wasconstructed. Air was initially passed through a wad of glass wool totrap solid particles, as well as oil droplets. Next, the air wentthrough a column filled with activated carbon to further clean the airstream. After the carbon filter, another glass wool wad trapped anycarbon particles that may have escaped the column. Sequential filteringsuch as this has been previously shown to generate halogen demand freeair.

Demand free air was channeled into a sparging tank filled with demandfree water. Air leaving the tank should have been saturated with water.This water rich air was used to strip chlorine from the solutions usedin the subsequent experiments. It was necessary to use water saturatedair for these experiments to minimize evaporative losses in the flaskscontaining the halogen solutions. Moreover, to increase the effect ofthe air stripping action, magnetic stirrers were used to continuallyagitate the solutions.

Chlorine was dosed into erlenmeyer flasks containing one liter of demandfree water (18 megohm resistance) at a concentration of 2 ppm. Ammoniumchloride concentration was 2 ppm. Unsubstituted glycoluril was added togive a final concentration of 1.2 or 5 ppm. Flask 1 contained chlorineand 5 ppm unsubstituted glycoluril, flask 2 contained chlorine and theammonium salt, flask 3 contained chlorine, the ammonium salt and 1.2unsubstituted glycoluril, and flask 4 contained chlorine, the ammoniumsalt and 5 ppm unsubstituted glycoluril. In flasks 3 and 4, the ammoniumchloride was added after the addition of the chlorine and glycoluril.The results are contained in Table V and FIG. 3.

                  TABLE V                                                         ______________________________________                                        Flask         Total Halogen ppm                                               ______________________________________                                        Time = 0                                                                      1             2.01                                                            2             1.96                                                            3             2.00                                                            4             1.99                                                            Time = 15 hr                                                                  1             1.96                                                            2             1.16                                                            3             1.10                                                            4             1.46                                                            Time = 19 hr                                                                  1             1.90                                                            2             1.03                                                            3             0.98                                                            4             1.43                                                            ______________________________________                                    

Adding unsubstituted glycoluril to Flask 1 decreased the volatility ofchlorine. Referring to FIG. 4, the solid line shows the first hours ofdata extrapolated to the 21st hour. This approximates the rate ofvolatilization of chlorine under experimental conditions. The dashedline demonstrates the effect of glycoluril. Unsubstituted glycoluril wasadded at the sixth hour and chlorine flashoff essentially ceased.

EXAMPLE 5

Aqueous solutions containing 2.5 ppm total available chlorine and 5, 10and 25 ppm unsubstituted glycoluril were prepared and tested over aperiod of 5 minutes for microbicidal activity in accordance with themethod of Example 2. The results of this test are depicted in FIG. 5,showing that the rate of biocidal activity in the solution of 25 ppmunsubstituted glycoluril is slower than the rate at 5 and 10 ppmunsubstituted glycoluril.

EXAMPLE 6

A further study was conducted to demonstrate the efficacy of chlorine asa disinfectant when stabilized with unsubstituted glycoluril alone orwith unsubstituted glycoluril and another chlorine stabilizer. As shownin FIG. 6, a solution containing 1.5 mg/l total available chlorineremains essentially equally efficacious as a disinfectant, whethercombined with 7 mg/l of unsubstituted glycoluril alone, or with 7 mg/lunsubstituted glycoluril and 50 mg/l isocyanuric acid (CYA).Unsubstituted glycoluril used in accordance with the present inventionat varying concentrations, as previously discussed, is an effectivestabilizer for the chlorine disinfectant and the chlorine remains aneffective disinfectant, either in the presence or absence of otherchlorine stabilizers.

EXAMPLE 7

The following example illustrates the effectiveness of glycoluril toinhibit the formation of trihalomethanes (THM) from humic acid. Testsolutions were prepared in 120 ml new vaccine bottles which were washedwith chromic acid cleaning solution, rinsed in hot tap water, and thenin distilled water before use. The following stock solutions wereprepared for use in these tests: a 200 ppm solution of availablechlorine from commercial bleach, a 0.1% humic acid solution (Humic acid,sodium salt; Aldrich Chemical Co., Inc., CAS #1415-93-6), a 0.04%unsubstituted glycoluril solution, and a 0.1% s-triazinetrione (CYA)solution. Thirteen solutions were prepared as outlined in Table VI.

                  TABLE VI                                                        ______________________________________                                        Preparation of Test Solutions                                                        ml of Test Stock Solution                                              Bottle   H.A.   Compd. G     CYA  Chlorine                                    ______________________________________                                        1        0.3    1.5          --   6                                           2        0.3    3.0          --   6                                           3        0.3    7.5          --   6                                           4        0.3    15.0         --   6                                           5        0.3    1.5          6    6                                           6        0.3    3.0          6    6                                           7        0.3    7.5          6    6                                           8        0.3    15.0         6    6                                           9        0.3    --           --   6                                           10       0.3    --           6    6                                           11       --     15.0         --   6                                           12       --     --           6.6  6                                           13       --     --           --   6                                           ______________________________________                                    

Each bottle was 3/4 filled with boiled glass distilled water, and thestock solutions were then added thereto. Each bottle was then filled tothe top with boiled distilled water, covered with a Teflon cap, andsealed with a metal vaccine crimp cap. The bottles were held at roomtemperature overnight and the next day were analyzed for the presence oftrihalomethanes. The solutions were analyzed for chloroform, bromoform,bromodichloromethane and dibromochloromethane, and the results are shownin Tables VII and VIII.

                  TABLE VII                                                       ______________________________________                                        Concentrations of Reactants in Solutions and the                              Resulting ppm Chloroform Assayed in each Solution                             ml of Test Stock Solution                                                                             Results                                               Bottle H.A.   Compd. G  CYA  Chlorine                                                                             (ppm CHC13)                               ______________________________________                                        1      15     5         --   10     0.015                                     2      15     10        --   10     <0.010                                    3      15     25        --   10     0.061                                     4      15     50        --   10     0.102                                     5      15     5         50   10     0.059                                     6      15     10        50   10     0.047                                     7      15     25        50   10     0.030                                     8      15     50        50   10     0.031                                     9      15     --        --   10     0.137                                     10     15     --        50   10     0.081                                     11     --     15        --   10     0.088                                     12     --     --        50   10     0.059                                     13     --     --        --   10     <0.010                                    ______________________________________                                    

                  TABLE VIII                                                      ______________________________________                                        Percent Reduction of Chloroform in Sample Compared                            to the Control, Solution 9, at 137 ppb                                        Bottle         ppb CHC13  % Reduction in THM                                  ______________________________________                                        1   15 HA, 5 G     15         89.1                                            2   15 HA, 10 G    <10        92.7                                            3   15 HA, 25 G    61         55.5                                            4   15 HA, 50 G    102        25.5                                            5   15 HA, 5 G, 50 CYA                                                                           69         49.6                                            6   15 HA, 10 G, 50 CYA                                                                          47         65.7                                            7   15 HA, 25 G, 50 CYA                                                                          30         78.1                                            8   15 HA, 50 G, 40 CYA                                                                          31         77.4                                            9   positive control                                                                             137        --                                              10  15 HA, 50 CYA  81         40.9                                            11  50 G           88         35.8                                            12  40 CYA         59         56.9                                            13  negative control                                                                             <10        >92.7                                           ______________________________________                                    

As the data reveals, except for chloroform, the THMs were below theminimum detection level of less than 0.010 ppm in all test solutions.Solution 13 was a negative control, containing only 10 ppm chlorine inboiled distilled water, and it had less than 0.010 ppm chloroform. WhenCYA alone (#12), unsubstituted glycoluril alone (#11) and CYA plusunsubstituted glycoluril together (#10) were added to the chlorinesolution, there were increases in chloroform to 59, 88 and 81 parts perbillion (ppb), respectively. This indicated that available chlorinereacted with these compounds or impurities in these compounds to formsome chloroform. The addition of only humic acid to the chlorinesolution (#9) gave the highest reading for chloroform of 137 ppb, andacted as the positive control.

Solutions 1-4 represented varying concentrations of unsubstitutedglycoluril in combination with 15 ppm humic acid and chlorine. Theresults indicate that 5 and 10 ppm unsubstituted glycoluril almostcompletely prevented chloroform formation, while 25 ppm only inhibitedformation by 55.5%, and 50 ppm unsubstituted glycoluril only resulted in25.5% reduction over the positive control. It is therefore shown thatlow levels of unsubstituted glycoluril (5 and 10 ppm) prevent chloroformformation from humic acid almost completely, while higher concentrationsinhibit THM formation but to a lesser extent. These results areexplainable on the assumption that an impurity in the glycolurilresulted in the formation of the chloroform. At 5 and 10 ppm levels, theimpurity was too low to form an appreciable amount of chloroform, whileat the higher concentrations there was sufficient impurities toappreciably affect the test. In any event, the tests do demonstrate theeffectiveness of unsubstituted glycoluril to prevent or inhibit theformation of THMs.

Solutions 5-8 represent varying levels of unsubstituted glycoluril with50 ppm CYA. This treatment group gave good reduction over the positivecontrol, and the results were consistent with varying concentrations ofglycoluril. There was some slight chloroform inhibition at 5 ppmunsubstituted glycoluril and greater inhibition at 10, 25 and 50 ppmunsubstituted glycoluril in combination with the CYA. Maximum inhibitionwas reached at 25 ppm, with no improvement at 50 ppm. Thus, the optimumunsubstituted glycoluril range is in the range of 10-25 ppm.

This test amply demonstrates a definite reduction of chloroform from thereaction of chlorine with humic acid when the treatment group containedboth CYA and unsubstituted glycoluril. There was about 41% reduction by50 ppm CYA alone, but as high as 78% reduction was found withcombinations of CYA and unsubstituted glycoluril. The combination of CYAand unsubstituted glycoluril was more effective at low concentrationsthan either compound by itself.

What is claimed is:
 1. A method for disinfecting an aqueous system whichcomprises:a. maintaining in the aqueous system a disinfectingconcentration of total available chlorine by adding a chlorine-sourcecomposition other than chloroglycoluril; and b. adding to the aqueoussystem an amount of a glycoluril-source composition sufficient tomaintain a concentration in the aqueous system of from about 0.1 toabout 40.0 ppm of glycoluril, said glycoluril-source composition beingselected from the group consisting of unsubstituted glycoluril,alkyl-substituted glycoluril and phenyl-substituted glycoluril.
 2. Themethod of claim 1 and which comprises maintaining a concentration offrom about 1.0 to about 10.0 ppm of glycoluril.
 3. The method of claim 1and which comprises maintaining in the aqueous system a concentration ofat least about 0.6 ppm of total available chlorine.
 4. The method ofclaim 3 and which comprises maintaining between about 1.0 and about 10.0ppm of glycoluril in the aqueous system.
 5. The method of claim 4 andwhich comprises maintaining between about 1 and about2 5 ppm of totalavailable chlorine in the aqueous system.
 6. The method of claim 1 andwhich further includes adding to the aqueous system a chlorinestabilizer in addition to the glycoluril-source composition, theadditional stabilizer being selected from the group consisting ofcyanuric acid, oxazolidinone, imidazolidinone, dimethylhydantoin,succinimide, toluenesulfonamide, sulfonamidobenzoic acid, melamine,dioxohexahydrotriazine, piperazinedione and azodicarbonamidine.
 7. Themethod of claim 1 and which comprises adding to the aqueous system afirst composition comprising said chlorine-source composition, andadding to the aqueous system a second composition different from thefirst composition and comprising said glycoluril-source composition. 8.The method of claim 7 in which said second composition consistsessentially of the glycoluril-source composition.
 9. The method of claim7 in which said chlorine-source composition comprises a compositionselected from the group consisting of: calcium hypochlorite, sodiumhypochlorite, lithium hypochlorite, sodium dichloro-s-triazinetrione,chlorine gas, potassium dichloro-s-triazinetrione,trichloro-s-triazinetrione, bromochlorodimethylhydantoin,dichlorodimethylhydantoin and hypochlorous acid.
 10. The method of claim7 in which said chlorine-source composition is physically combined withsaid glycoluril-source composition and said adding comprisessimultaneously adding both compositions to the water.
 11. The method ofclaim 7 in which said chlorine-source composition is physically separatefrom said glycoluril-source composition and said adding comprisesseparately adding said chlorine-source composition and saidglycoluril-source composition.
 12. The method of claim 11 in which saidadding of the chlorine-source composition comprises providing asolid-form material containing the chlorine-source composition,contacting the aqueous system with the solid-form material in a mannerto effect erosion of the solid-form material, and gradually eroding thematerial to introduce the chlorine-source composition into the aqueoussystem.
 13. The method of claim 12 in which the chlorine-sourcecomposition is selected from the group consisting of: calciumhypochlorite, lithium hypochlorite, sodium dichloro-s-triazinetrione,potassium dichloro-s-triazinetrione, bromochlorodimethylhydantoin,dichlorodimethylhydantoin and trichloro-s-triazinetrione.
 14. The methodof claim 12 in which said solid-form material further comprises aglycoluril-source compound selected from the group consisting ofglycoluril, alkyl-substituted glycoluril and phenyl-substitutedglycoluril.
 15. The system of claim 14 in which said solid-form materialincludes from about 50.0% to about 99.99% of the chlorine-sourcecomposition and from about 0.01% to about 50.0% of the glycoluril-sourcecompound.